Why is silk so expensive?

Why is silk so expensive?

Answer:

Silk is so expensive because a lot of labour is required to make silk.

Silk is formed from threads of silkworm cacoon , which is a labour intensive process. 

The process looks something like this

1. First the cocoons are weighed and sorted
2. Then the fibers are soaked in boiling water to unravel them and kill the larvae
3. Those fibers are strung onto spools. 
4. Finally, these spooled fibers can be made into silk fabric.

Also, silk was considered a precious resource since the time of Shakespeare, and it was always associated with luxury , which drove the price of Silk even further